This invention relates to a mechanism for forming spring pitch and, more particularly, to a spring-pitch forming mechanism in which a spring of the type that expands and contracts in the axial direction thereof is formed to have a desired pitch.
A mechanism for bending wire material in a spring manufacturing apparatus generally is of two types. One is a mechanism in which the wire material is wound upon a winding shaft moved in the axial direction while being rotated, and the other is a mechanism in which the wire material is supplied to a prescribed point tool and forcibly bent by the tool.
The former is suitable for the manufacture of a torsion spring (mainly a spring whose two ends have straight legs), and the latter is suitable for the manufacture of springs that contract or expand.
In the latter mechanism wherein the wire material is supplied to the point tool and forcibly bent, there are two means available for providing a spring with pitch while it is being manufactured. The wire material bent by the point tool is formed into a helical shape having a prescribed diameter in dependence upon the position and orientation of the point tool, but each coil of the wire material is in intimate contact with its neighboring coils.
One of the means for providing pitch mentioned above is to forcibly insert a sharp member between the coils of the wire material while the coils are being produced. This shall be referred to as the "wedge method" hereinafter. The insertion of the member is performed a single time in synchronism with the manufacture of a single spring.
In the other means for providing pitch, the wire material, immediately after it has been bent by the point tool, is forced out in a direction perpendicular to the plane in which the wire material is bent. This shall be referred to as the "pushing method" hereinafter. The pushing of the wire material is performed one time in synchronism with the manufacture of a single spring.
Accordingly, a user who manufactures springs with the wedge method is provided with a spring manufacturing apparatus that relies upon the wedge method, and a user who manufactures springs with the pushing method is provided with a spring manufacturing apparatus that relies upon the pushing method.
Recently, a single spring manufacturing apparatus capable of manufacturing springs using both of these pitch forming methods has been developed and several types of such apparatus have appeared. However, though these apparatus seem to enable manufacture in which the wedge and pushing methods are combined, the driving sources for driving these systems are independent of each other, as a result of which an increase in the size and cost of the apparatus cannot be avoided. Moreover, since the driving sources that make possible operation in the wedge and pushing methods are situated within the inner reaches of the apparatus, the mechanisms that transmit the driving forces from these sources to the spring manufacturing area inevitably are of a complicated nature. Complicated machinery makes it difficult to manufacture highly precise springs. The reason for this is that when a large number of mechanical parts intervene between the driving sources and the spring manufacturing area, overall play or backlash is amplified to a significant degree even if play or backlash of the individual parts is negligible.